She is researching human memory

Hedvig Söderlund, Professor of Psychology, is doing research on how human memory is organised in the brain.

Photograph: Mikael Wallerstedt

Hedvig Söderlund has recently been appointed professor of psychology with a focus on human memory. She is investigating, for instance, how gender, ageing and severe depression affect memory.

“To be more specific, I am investigating how episodic memory and spatial memory are organised in the brain and, in particular, how the part of the brain called the hippocampus is involved in episodic and spatial memory,” says Hedvig Söderlund, Professor of Psychology.

Episodic memory consists of personal and specific incidents at a certain time and place and it links together the thoughts, feelings, sounds and smells that a person has experienced on a specific occasion. Spatial memory can be described as how people make their way from A to B, like a sense of direction.

“Thanks to episodic memories, we know what we have experienced during our lives and who we are. But our episodic memory is more sensitive to disease, stress and ageing. One of the reasons for this is that episodic memories are complex and consist of numerous memory details stored in different places in the brain.”

Vital central area for memory

The hippocampus links together all the different memory details and knows where they are stored in the brain. This area is located in the central area of the brain and is important for both episodic and spatial memory.

“The hippocampus can be divided into different parts with different memory functions. The rear parts are particularly important for spatial memory, i.e. how places are associated with each other. The further back you go in the hippocampus, the more image details there are. The front parts, especially the left hippocampus, are important for linguistic details.”

Söderlund is also studying how episodic and spatial memory are affected by different factors, for example, gender, ageing and severe depression.

“When it comes to gender difference, the most noticeable difference is that men, as a group, have better spatial memory than women as a group.”

Researching brain activity

All differences are of course statistical differences between experimental groups, not individual differences.

“We are studying brain activity by using magnetic resonance after asking people to retain their orientation in a virtual labyrinth. We can then see that men activate the rearmost region of the right hippocampus to a much greater extent than women do. As a group, women activate the left hippocampus to a greater extent and seem to use a more linguistic strategy when doing the test.

From a group perspective, women have better episodic memory than men do but the difference is not as great as that with spatial memory.

Testing patients’ memory function

Söderlund is currently investigating, among other things, how memory is affected when patients with severe depression are given ETC (electroconvulsive treatment). Some patients have testified that they have suffered memory loss but so far research has not been able to prove the same degree of impact on memory.

“This could be because the patients’ episodic memory has not been tested sufficiently; instead, the focus has been on knowledge memory which is more robust. So far, we have been able to establish that before receiving treatment, people with severe depression have impaired episodic memory but relatively intact knowledge memory. It remains to be seen how the situation is after treatment.”